Quinones play an important role in a large number of biological electron transfer processes involving complexed metal ions. To understand the coordination chemistry of oxidized and reduced quinone ligands, studies have been carried out on simple well defined complexes. Semiquinone complexes of first row transition metals have been investigated structurally, magnetically, and electrochemically. Catecholate complexes of Mo(VI) show a unique tendency to undergo oxygen atom exchange reactions. Electron transfer reactions involving reduced and oxidized complexes with unsaturated substrate molecules are under investigation. Electron transfer in these systems can occur either by direct attack at the metal or by pi complexation with quinone ligands. The anticancer activity of metal complexed quinone drug molecules is under investigation. Preliminary results indicate that ferric complexes show decreased toxicity without a decrease in drug activity.